Non-clogging typewriter ribbon



United States Patent 3,110,386 NGN-CLOGGING TYPEWRITER EON Qharles C Rainas, 8 .33 W. 32nd, Austin, Tex. No Drawing. Fiied Sept. 12, 1969, Ser. No. 55,177 10 Claims. (Cl. 197-172) This invention relates to a ribbon for a typewriter or similar business machine which does not clog the type even after long periods of use and to a novel ink composition adapted for use with such ribbons.

In all types of ofiice machines such as typewriters, calculating machines, cash registers, time clocks and the like which utilize printing means including an inked ribbon, the depressions in the faces of the type gradually fill up with dried ink in admixture with dust and fuzzy fibers from the paper ad the ribbon. Then the depressions containing the dried gummy material are often cleaned using strong solvents, wire brushes, and sharp pointed instruments, which not only is messy and time-consuming but also can be quite injurious to the faces of the type. The inks normally used on ofice machine ribbons comprise as vehicles various mineral oils, fatty acids such as oleic acid, and various triglycerides such as lard oil and vegetable oils With a relatively low degree of unsaturation. The inks are formulated to be freely fluid at operating temperatures so as to transfer freely to the paper, becoming rapidly absorbed by the paper, and continually redistributed throughout the ribbon by capillary action to maintain high uniformity of inking for the entire service life of the ribbon. These vehicles are considered in the art of paint and ink formulation as non-drying vehicles and under the conditions of quiescent exposure to the air found in other types of usage they would remain liquid for many months or years. However, I have found by experiment that under the conditions of normal usage on a typewriter ribbon that such vehicles do oxidize and polymerize and engage in other reactions which result in the production of a gummy adherent mass on the type faces. It is believed that these reactions are speeded up by the following circumstances:

First, the ink in the ribbon, being spread over the fiber surfaces throughout the ribbon, behaves as if it has a much larger surface area than the simple superficial area of twice the width of the ribbon times its length.

Second, the ribbon is well aerated by being passed through the air and re-wound as many as ten to twenty times an hour while being used.

Third, this effect is much increased in local areas of the ribbon by the high-velocity impacts of the type faces. Such impacts not only cause vigorous mixing action, exposing new zliquid surfaces to the air, but also compress air trapped by enclosed regions of the type faces and force it through the ribbon. In addition, there may be instantaneous flashes of higher temperature due to the momentary high pressures produced by the impacts and the energy dissipated. All of these actions tend to increase the rate of reaction of the ink with the oxygen in the air, in accordance with principles well known in chemistry.

Fourth, the ink transferred from the ribbon to the type face is exposed to the catalytic action of the metal type face. Iron, copper, nickel, and many other metals are known to dissolve slightly in the presence of organic acids and other compounds to form metal-organic compounds which are highly active in catalyzing oxidation and polymerization even when present in concentrations as low as a few parts per million. All the above actions apparently combine to produce an effect sufficiently vigorous that it produces oxidation not only of the unsaturated organic acids and glycerides present, but also apparently some of the constituents of the mineral oils iildfi dfi Patented Nov. 12, 1263 "ice used may also react. This conclusion is based on careful observation of the progress of normal and accelerated tests, but an exact chemical analysis of the reactions involved and their products would be very diflicu l-t because of the complex mixtures involved.

The practical results of the above effects and reactions may be summarized as follows: The ink in the ribbon becomes initially oxidized but not polymerized and remains fluid. Only in rare cases does a machine stand unused for weeks or months so that the ink in the unwound portion of the ribbon reacts with the air so that it becomes polymerized and will no longer transfer an adequate marking to the paper, but some examples of such behavior have been observed. Evaporation of the vehicle is not believed to play a major role in these effects-for example, unpigmented oil stains on paper are seen to persist for many years without volatilizing and thus disappearing. Normally, a thin film of oxidized fluid ink is transferred to the face of the type with some admixture of dust and fibers, but as long as the machine is in operation, little polymerization occurs. When the machine stands unused for a few hours, overnight, or over the weekend, some of this film polymerizes to form a gummy, tenacious, adherent material which may not be dislodged by the next usage of the machine. In this way material is built up on the type faces in successive cycles of use and non-use until the material starts printing an unwanted impression and the type is said to be clogged.

From the above discussion it will be seen that it is impossible to set up a highly accelerated test for clogging of type by various ribbons, since the clogging is not a simple function of the number of type face impacts on the ribbon but is the result of a complex pattern of periods of usage and non-usage combined with other variable factors. For example, a certain commercial type of ribbon was known to produce clogging with about 4,000 or more impressions each of the characters "a, e, and 0 over a period of a Week or two, and with much fewer impressions over a period of one or two months. However, when such a ribbon was placed on an electric typewriter with an automatic repeat key, over 70,000 impressions were made from one type face in the time of about three hours with no clogging of the type. A mixture of ink and fibrous material accumulated early in the test in the enclosed regions of the type face, but it never became sufficiently adherent and coherent to print clogged. Periodic examination of this material under a microscope showed that the ink remained completely fluid, serving as a lubricant for the dust and fibers rather than as a strong binder. For these reasons, all the significant performance tests made in the development or" this invention had to be made under conditions resembling normal usage and for extended periods of time which ranged from one week to six months.

The object of my invention is to provide an inked ribbon which does not produce gummy adherent deposits on the type faces and which minimizes all accumulations on the type faces which might interfere with their function. The ribbon of the invention reduces periodic cleaning to a minimum since the amount of ink transferred and remaining adherent to the type faces does not increase throughout the life of the ribbon. Any ink which is deposited is of such a nature that it remains fluid and fresh in consistency so that it does not bond to the type faces and can be readily removed with a soft brush. At the same time, the adhesion of the ink to the paper is not noticeably affected in the preferred ranges of ink composition. This is a surprising result, since it would usually be expected that if the ink failed to adhere cumulatively to the type faces, it would show decreased adhesion to the paper, to some extent at least. I have also found that ink deposited by the ribbon of the invention can be hesive to the type faces.

erased just as readily as the ink from conventional ribbons. This object is achieved in accordance with the present invention by admixing a silicone oil with the ink in the ribbon. The addition of the silicone oil reduces adhesion of oxidized ink to the metal type faces and prevents layer after layer of polymerized ink from building up. In other words, the aged ink compounds, which are formed in greatly decreased amount, are neither cohesive nor ad- The protection of the performance of the type in this manner is achieved effectively, simply, and inexpensively. Silicone oil may be added to the fabric from which the ribbon is made before impregnation with a conventional ink, it may be added to the ink used with untreated fabric, or it may be added to ribbons which have previously been impregnated in the usual manner.

The silicone oils suitable for use in this invention comprise those fluids commercially available from several manufacturers under trade designations such as silicone fluids, silicone oils, methyl silicone oils, and similar terms. These materials include specifically polydimethyl siloxanes, polymethylphenyl siloxanes, and polydiethyl siloxanes. There is another common silicone fluid, methylhydrogen siloxane, which is usually included in the group known as silicone fluids but this material is not suitable for use in the present invention because it is unstable and reactive with water at room temperatures and because it becomes bonded to the fibers of the ribbon and then is no longer available as a fluid component of the ink. The silicone fluids have viscosities ranging from to over 10,000 centistokes, but the fluids preferred for use in this invention range from 100 to about 3000 centistokes. The viscosity as well as other characteristics depends on the degree of polymerization. Suitable silicone fluids are further characterized by a high degree of chemical inertness, low vapor pressure at room temperatures and consequent very low volatility, non-hygroscopic and nonreactive with Water and water vapor at room temperatures, not subject to continued polymerization or depolymerization under ordinary conditions, with very low mutual solubility with any of the oils, fatty acids, and other nonvolatile liquid materials commonly used in the formulation of typewriter ribbon inks. In this specification the operable materials as defined above are designated as stable silicone oil, and in some of the claims the above defining clauses are summarized in adjectival form in the term inert non-volatile medium-viscosity non-hydrolyzing non-gumming immiscible stable silicone oil. It will be understood that these restrictions apply to the behavior of the various silicone oils under conditions of normal usage in the typewriter ribbons, and do not refer to laboratory tests using high sustained temperatures, special chemical reagents, and the like treatments which can cause changes in even the most stable silicone oils available. For a discussion of silicone fluids and their properties, especially those that are currently commercially available, reference may be had to eilicones and Their Uses by Rob Roy McGregor (McGraw-Hill, 1954).

A stable silicone oil may be added to a standard typewriter ink formulation while it is being milled, but in most cases it is quite difficult to stabilize the emulsion so produced so that separation of the stable silicone oil does not occur during storage, sometimes prolonged, of the ink before application to the ribbon. It is generally much less trouble to disperse the stable silicone oil in the ink immediately before addition of the mixture to the ribbon inking machine. I have found that the stable silicone oil does not disperse well in the ink by ordinary high-speed stirring methods but instead forms globules of widely varying size so that the stable silicone oil begins to separate out upon standing for as short a time as 10 minutes. However, when the stable silicone oil is added to the ink in a standard paint can or similar container and then shaken in a machine of the sort widely used in retail paint stores for remixing paint at the time of sale, then in a few minutes mixing a good uniform emulsion is formed that does not begin to separate noticeably for one or two days, which is more than adequate stability in the ribbon inking machine. A typical machine suitable for this mixing that has been used successfully and is widely available is called Red Devil Paint Conditioner and is manufactured by Red Devil Tools, of Union, New Jersey. This machine subjects the container to a peculiar combined twisting and shaking motion at high speed that is very highly effective in m'ming and emulsifying.

A preferred method of manufacture of ribbons under this invention resembles the usual process in every respect except for the use of ink which has been emulsified with a suitable amount of stable silicone oil. The fabric ribbon which has been made or purchased ready for inking is advanced through the emulsified ink. The excess ink is removed by passing through squeeze rolls or between scrapers with pressures 30 adjusted as to leave a quantity of ink in the ribbon which will produce the desired depth of impression in use. The amount of ink absorbed and remaining in the ribbon varies with the thickness of the fabric and the fibers composing it. As an example, a cotton ribbon 0.0043 inch thick by inch Wide by 12 yards long will retain about three grams of ink. The presence of the stable silicone oil in the ink reduces ad hesion of the ink to the type faces in the course of extended usage, and if the ink does oxidize and polymerize, the hardened particles remain dispersed by the stable silicone oil and do not adhere to the type faces. In addition, there is some evidence that the stable silicone oil may act to inhibit or prevent the oxidation and polymerization of the ink to a considerable extent. The result is that the ink in combination with dust and lint never forms a hard adherent cake on the type faces When the stable silicone oil is present.

If desired, the stable silicone oil may be sprayed or otherwise applied to the surface of a ribbon which has been inked previously. If desired for convenience in more uniform application, the stable silicone oil may be diluted with a volatile solvent which afterward disappears from the ribbon-for example, a 10% solution in trichloroethylene has been used. When stable silicone oil has been applied to the surface of an inked ribbon, a very short period of usage is sufficient to cause it to be dispersed evenly and uniformly throughout the ribbon, even though the initial application of stable silicone oil is rather irregular and uneven.

Another practicable manner for adding the silicone oil to the ribbon is by treating the uninked ribbon with the stable silicone oil or with a solution or dispersion of a stable silicone oil. On subsequent inking with a normal type of ink the stable silicone oil becomes satisfactorily dispersed throughout the ribbon, even though the previous application of stable silicone oil was quite irregular or uneven.

The ribbons suitable for use in connection with this invention are woven or non-woven bibulous fabrics which are porous completely through and which have the ability to carry fluid ink by capillarity. The fibers may be cotton, rayon, silk, nylon, or similar natural or artificial materials. After the type face has struck the ribbon and forced some of the ink out of the ribbon onto the paper, the fibers of the ribbon have the ability to reabsorb ink from adjacent portions of the ribbon and thus preserve uniformity of inking and secure repeated and extended service life for the ribbon. A thin flexible tough porous strip of plastic or other material with the same performance characteristics as described for the fabric ribbon would also be suitable for use under this invention. However, this invention does not apply to ribbons of the carbonpaper type which have ink only on the side which contacts the paper and have an effectively impermeable surface on the side which contacts the type face. Likewise this invention does not apply to any so-called inks which are based on wax and other materials and which are substantially solid at room temperatures and are used for coating carbon paper and other transfer sheets.

The stable silicone oil should be added to the ink or the ribbon in a quantity equivalent to from about /2% to 20% by weight of the ink and preferably between 2% and 6%. For the different formulations of ink the optimum and economical amount may vary within the ranges suggested. If less than /2% is used the desirable eifect is not attained to any useful extent. Above 10%, little advantage is gained in ordinary usage, the cost is considerably increased, and the stable silicone oil may have to have coloring matter separately dispersed in it in order to avoid a loss of depth of color in the impression printed due to a dilution effect.

Example I A standard grade uninked cotton typewriter ribbon was impregnated with an ink made in accordance with the formulation set forth below in admixture with 4% by weight of polydimethyl siloxane of 350 centistokes viscosity (DC 200-350 Silicone Fluid made by Dow Corning Corporation, Midland, Michigan):

Parts by weight Mineral oil (100 visc. Ink Gib-Texaco) 64.0 Oleic acid (Emery Industries, Cincinnati) 14.8 Nigrosine Base (Hilton-Davis Chemical Co.) 7.4

Green Toner No. 2038 (Brooklyn Color Works) 1.8 Pure Blue Toner (Hilton-Davis Chemical Co.) 0.5 Purple Base 2-B (National Aniline) 0.5

Peerless Beads (Columbia Carbon Co.) 11.0

The materials listed in the above formulations are readily available on the market, and equally suitable materials can be secured from other suppliers under different names. This formulation is considered to be a typical black ribbon ink and is similar to that supplied by various ink manufacturers for use by typewriter ribbon manufacturers.

Ribbons so prepared, placed in service with slow intermittent usage, show no clogging of the type faces over periods of 3 to 6 months service. The type may be brushed briefly with a soft bristle brush about once a month and no further cleaning seems ever to be required. All tests indicate that the printing capacity of the ribbon can be exhausted without any clogging, and that the service life of the ribbon is somewhat increased, especially at the lower rates of usage.

Example 11 A typical example illustrating the invention in conjunction with a blue ink composition is as follows:

Parts by weight Mineral oil (100 visc. Ink Oil-Texaco) 33.0 Lard oil (Armour) 23.0 Oleic acid (Emery Industries) 13.2 Victoria Blue B Base (Hilton-Davis Chemical Co.) 4.4 Blue Lake (Ansbacher-Siegle Corp.) 22.0 Milori Blue (H. Kohnstamm & C0.) 4.4

To ink milled to the above formulation was added 6% of polymethylphenyl siloxane of 500 centistokes viscosity (DC 510500 Fluid, Dow Corning Corp, Midland, Michigan) with about 25% phenyl groups, and the whole emulsified with the Red Devil Paint Conditioner for five minutes. The ribbons impregnated with this ink gave satisfactory performance with no clogging in the same fashion as described before.

In the case of duplex or two-colored ribbons in which one half of the ribbon longitudinally is impregnated with one color (commonly black) and the other half of the ribbon is impregnated with another color in a vehicle which is not miscible with the first ink (commonly red in a castor oil and tricresyl phosphate vehicle), it has been found that stable silicone oil can be added to either or both inks without causing any difliculties, since the stable silicone oil is not soluble in either vehicle and consequently causes no migration or mixing of colors.

From the foregoing description it will be apparent that the addition of the stable silicone oil to the ink provides a definitely improved typewriter ribbon which can be produced at a relatively small increase in cost. Any desired variations in the composition and the method of preparing the ribbon will be apparent and can easily be vmade by those skilled in the art. The specific examples cited herein are not to be construed as limiting the invention except as necessitated by the scope of the appended claims.

I claim:

1. An inked ribbon adapted for use with printing means, comprising;

a bibulous, flexible ribbon;

a fluid ink impregnating said ribbon;

and a non-hydrolyzing silicone oil impregnating said ribbon.

2. The article of claim 1 wherein said silicone oil cornprises at least one member of the group consisting of, polydimethyl siloxanes, polymethylphenyl siloxanes, and polydiethyl siloxanes.

3. The article of claim 1 wherein said silicone oil is present in an amount between about /2% and 20% by weight, based upon the weight of said ink and has a viscosity between about 20 and 10,0000 centistokes.

4. An improved typewriter ribbon comprising;

a ribbon of fibrous flexible material;

a fluid ink coating said ribbon and comprising a coloring and an oily vehicle carrying said coloring;

and a non-hydrolyzing silicone oil admixed with said ink.

5. The article of claim 4 wherein said silicone oil comprises at least one member of the group consisting of, poly-dimethyl siloxanes, polymethylphenyl siloxanes, and polydiethyl siloxanes.

6. The article of claim 4 wherein said silicone oil is present in an amount between about /2 and 20% by weight, based upon the weight of said ink and has a viscosity between about 20 and 10,000 centistokes.

7. An improved typewriter ribbon comprising;

a ribbon of fibrous flexible material;

and an admixture comprising, an oily vehicle, a coloring and a non-hydrolyzing silicone oil, said admixture coating said ribbon.

8. The article of claim 7 wherein said silicone oil comprises at least one member of the group consisting of, polydimethyl siloxanes, polymethylphenyl siloxanes, and polydiethyl siloxanes.

9. The article of claim 7 wherein said silicone oil is present in an amount between about /2% and 20% by weight, based upon the weight of said ink and has a viscosity between about 20 and 10,000 centistokes.

10. A ribbon which, when inked, is suitable for use on typewriters, calculating machines and like business machines, comprising a thin ribbon strip of flexible materal havng throughout its length the bibulous characteristics of woven and non-woven fabrics; and

a non-hydrolyzing silicone oil dispersed within the pores of and contained by the material of said ribbon strip,

said ribbon strip being capable of carrying a fluid ink by capillarity, said silicone oil being capable of modifying fluid ribbon inks to reduce clogging of the type during use of the ribbon after the ribbon has been inked.

References Cited in the file of this patent UNITED STATES PATENTS 2,036,471 Gill Apr. 7, 1936 2,139,092 Ncidich Dec. 6, 1938 2,866,711 Hart Dec. 30, 1958 2,872,356 Bull et a1. Feb. 3, 1959 

1. AN INKED RIBBON ADAPTED FOR USE WITH PRINTING MEANS, COMPRISING: A BIBULOUS, FLEXIBLE RIBBON; A FLUID INK IMPREGNATING SAID RIBBON; AND A NON-HYDROLYZING SILICONE OIL IMPREGNATING SID RIBBON. 